Dehydrogenation catalyst



motor fuels, and

Patented Nov. 4, 1941 .DEHYDROGENATION CATALYST Walter. F. Hnppke,Lomita, Calif., assignor to Union Oil Company of California, LosAngeles, Calif., a corporation .of California No Drawing. ApplicationSerial No.

(Cl. 252-210) tion further comprises uranium oxide in com- 14 Claims.

This invention relates to catalysts and the production of such catalystshaving high activity for catalytic dehydrogenation or kindred catalyticprocesses and the like, for example for the dehydrogenation ofisobutane, n-butane, propane, cyclohexane and similar materials wherebyunsaturates and aromatics and the like may be obtained for the purposesof production of solvents,

similar substances.

I have discovered that uranium oxide or vanadium oxide, when used inconjunction with other appropriate materials, is a highly valuabledehydrogenating catalyst for the dehydrogenation of various organicmaterials, such as isobutane, n-butane, propane, cyclohexane and similarmaterials obtained from petroleum. I have also discovered, however,that, while uranium oxide or vanadium oxide is a highly active agent forthese purposes, it does not function emciently if used alone, and itbecomes desirable if not necesary to employ it in conjunction withanother material which serves to disperse the uranium or vanadium oxideand to impart body and a suit-.

able gel-type structure of a more or less vitreous character. For thispurpose, aluminum oxide,

zirconium oxide or thorium oxide, or mixtures of these, may be employed.Again greater efli- 'ciency may be obtained by employing, in additionto,-, the dispersing or bodying agent, an agent to I .activate andprolong the life of the catalyst. For thisj purpose, zinc oxide isoutstanding in that it imparts much longer life to these catalysts heredescribed and tends to increase their efficiency andthe rate ofconversion.

It' be noted, therefore, that the most satisfactory catalyst accordingto this invention, comprises three types of constituents as follows: (1)The primary or active agent in the form of uranium oxide; (2) adispersing and bodying agent or distender for the catalyst having theproperty of imparting a more adequate gelatinous or "gel structure suchas aluminum, zirv conium, or thorium oxide or mixtures of these oxides;(3) an agent to activate and prolong the lifeof the catalyst,particularly zinc I oxide.

' Either the oxide for dispersing the catalyst or the activating andlife-prolonging agent may be omitted or both may be omitted, where it isdesired to dispense with either or both of their functions.

' Broadly stated, the invention resides in a catalyst comprising uraniumoxide and a dispersing bodying agent for increasing the gel character ofthe catalyst, of which aluminum, zirconium and thorium oxides comprisethe class. The inven- January 8, 1937, 119.629

bination with an oxide such as zinc oxide to increase the life of thecatalyst, both where a dispersing and bodying oxide is included andwhere it is not included.

Aside from those aspects of the invention outlined above, I have alsodiscovered that vanadium oxide is ordinarily a good substitute foruranium oxide as the primary or active agent. Where vanadium oxide isemployed, the other constituents of the catalyst will be employed in thesame respects as above described with respect to uranium oxide, zincoxide being used as the added promoting or activating or life-prolongingagent and aluminum, zirconium and thorium v oxides being used as bodyingor distending agents. The invention therefore also resides in catalystswhere either of the group consisting of vanadium oxide and uranium oxideis used as the principal catalyst, in conjunction withthe dispersing orbodying agent or with the activating or life-pro-' longing agent, orwith both types of agents. The invention also extends to a mixture ofuranium and vanadium oxides as a catalyst, with or without the othertypes of agents.

In a preferred form of the invention the reduced forms of uranium andvanadium oxides are preferred as being more eflicient. The reason forthis preference is that in-the presence of hydrocarbon gases to betreated in the presence of the catalyst, for example for dehydrogenationpurposes, when the higher oxide forms are used they are readily reducedand in many instances the oxygen acts upon the hydrocarbons to formobjectionable materials, such as gummy constituents which contaminatethe catalysts and greatly reduce their efliciency. Of course ininstances where such objectionable materials are not produced or do noteffect the catalyst, the higher oxide form could beemployed.

Considering the practice of this invention, the oxides mentioned may beproduced in various ways. The preferred procedure resides inprecipitating the hydroxides (or perhaps more properly the hydrousoxides) from solutions of the salts of the metals being employed, thisprecipitation being preferably effected with ammonium hydroxide. Forexample, solutions of mixed nitrates or chlorides of the various metalsinvolved are commingled with ammonium hydroxide solution whereby thecorresponding hydrated oxides are precipitated. More specifically, suchsoluble salts of the metals are dissolved in water to yield about a 2%solution. This solution usually will gel.

aqua ammonia slowly added until precipitation is complete. Most of thesehydrous oxides are precipitated in the pH range of 3 to 5. Thesupernatant liquid is drawn ofl- 'as the precipitate is settled and theslurry is then transferred to a Buckner funnel or the like andrepeatedly washed or filtered until no more electrolyte can be removed.At this point the material usually tends to remain in suspension infinely divided form when stirred into water, and when in this ilne statemay be termed peptized."

These gelatinous precipitates are very adsorptive and by reason of thatcharacteristic may have a small amount of a promoter added thereto insome other form than the form of these gelatinous precipitatesthemselves. should it be so desired. For example, if a vanadium ortitanium salt had not been employedin the precipitation or the hydrousoxides, ammonium metavanadate or uranyl chloride solution may be stirredinto the gelatinous mass or salt will be adsorbed or absorbed by thecarrier This procedure may be employed as a means to add the principalcatalyst to the mass. or to add the second principal catalyst thereto ifboth uranium and vanadium are to be employed.

After the gelatinous hydrous oxide precipitate has been prepared, thefilter cake is allowed to dry at temperatures around 135 to 150 F. untilhard vitreous lumps form. In this drying operation, the gel shrinks toabout 5 to of its original wet volume. The lumps so obtained are thenbroken up and screened, preferably to pass 10 mesh but to stay on 9. 20mesh screen. These gel granules are then heated up to temperatures inthe order of 650 F. in a large electric tube heater and dry air isslowly passed thereover. With this treatment the gel will shrinkapproximately onethird more and reach its final volume.

In this form the catalyst constitutes a mixture of higher oxides ofuranirrmand/or vanadiunrand zinc or such of these as nay be oye'd suchoxides being distributed throughoutthe aluminum, zirconium or thoriumcarrier oxide.

The irreducible refractory oxides, that is those of aluminum, thoriumand zirconium, serve to some extent as diluents of the other oxides butare chiefly used because they improve the physical characteristics ofthe catalysts. These oxides all yield gelatinous precipitates whendilute ammonia is added to a dilute solution of their soluble salts.They dry slowly to a hard vitreousgel. These gels adsorb gases withgreat avidity, a very excellent property in the catalyst. When it isdesired to incorporate in such a catalyst another ingredient, which ofitself does not form gelatinous hydrous oxides, such a gelatinoushydrous oxideof the other ingredient is invariably obtained whenco-precipitated with said refractory hydrous oxides. Also, as aboveindicated, such gelatinous hydrous oxides, when sufiiciently suspensionwhereby the washed to remove all electrolytes are then capable ofadsorbing in the cold appreciable quantities of other electrolytes whichmay be desired in the finished catalyst. In addition to those mentioned,vanadyl chloride and nitrate and uranyl nitrate and the like may bestirred into the gel as above described. The gel is then dried. The sameoxides are obtainable by heating the dried gel when these solutions areadsorbed in the gel as when originally precipitated with the carrierhydroxides. Other catalytic agents than uranium and vanadium compoundsmay be adsorbed in gels in the same manner, and a dried gel recovered,which may be used in that form where appropriate, or heated to convertthe salt when required. This procedure is particularly desirable for allthose catalytic metals which do not easily form insoluble hydrates,which class includes uranium and vanadium. Salts of those metals may bedeposited, not only in aluminum, zirconium and thorium gels which areprecipitated easily by. aqua ammonia from solutions or their salts. butalso in the gel of any other metal whose salts readily precipitategelatinous insolu ble hydrates with aqua ammonia.

For some uses it is possible to use the catalyst in the form as producedby the steps above described, the uranium and vanadium oxides being ofthe higher oxide form. However, for many purposes, if not for mostpurposes, it is desirable to use catalysts in which such of the uraniumand vanadium oxides'as are present are in the reduced form, for thereason that in the presence of hydrocarbon gases the higher oxides passto the reduced form and the oxygen acts to form objectionable materialssuch as gummy compounds which damage the catalysts and greatly reducetheir value. if

Therefore in order to obtain the most generally useful form'of catalyst,the hard dry gel obtained after drying at 650 F., as above-described,"is reduced. with hydrogen as byplacing the gel in a Pyrex orsilica tube and passing dry hydrogen gas therethrough while thetemperature is being raised to about 850 F. The reduced catalyst thusobtained, without having had access to oxygen, may be then employ ed toperform its catalytic function. For example, its'temperature may beestablished at any desired operating degree, such as 850 F., and a gaspassed therethrough for dehydrogenation thereof, such as isobutane orpropane or cyclohexane or other appropriate gas.

In preparing 'a' catalyst according to this invention, the proportion ofthe materials used may -,...b e varied very widely. According to asatisfactory procedure, a'catalyst consisting of uranium or ,vanadiumoxide, aluminum or zirconium or thorium oxide and zinc oxide may beprepared employing roughly equal mol proportions, or in other wordsportions running about 30 to 40 percent each of such a three unitmixture.

As an example of the value of a catalyst according tothis invention, andas an example as to the use to which such a catalyst may be put,isobutane or cyclohexane or other material adapted to dehydrogenationmay be passed in, gaseous form through a catalytic body at a temperatureof 850 F. or 950 F. at a rate averaging one second contact time. Therate however will range from a small fraction of one second to possiblyseveral seconds according to the materials being treated and theconditions.

Working under conditions such as these, catalysts of the nature abovedescribed have relatively high activity for relatively great lengths oftime at reasonable temperatures. For example, a three-constituentcatalyst as here described, containing uranium oxide or vanadium oxidein a reduced form, when operating at a temperature of about 850 F. willhave a life of about 8 to 10 hours with a maximum conversion onisobutane of about 18%. Under these conditions if the promotingcatalyst, that is zinc oxide, is omitted, a maximum conversion of about15% is obtainable or a reduction of 15% to 20% in activity. Again, ifthe temperature for the three component catalyst is increased to about950 its life will be decreased to about 1 to 2 hours, but the conversionratio will be stepped up to about 30%; and if the operating temperature.is increased to 1050 F. the conversion ratio will be nearly doubled butthe life of the catalyst will be still further reduced. In each of theseinstances the presence of 30% to 60% of zinc oxide ordinarily increasesthe life of the catalyst from 2 to 3 times what it would be in theabsence of the zinc oxide.

Thus, from the above statements, it will be apparent that while acatalyst containing only uranium or vanadium oxide and one of thedisoxide is good in general as a catalyst, its life nevertheless isroughly only one-half to onethird that of the catalyst containing zincoxide and its activity is around 15% to 20% less than that of thecatalyst containing zinc oxide. 01

' course, it is possible to use uranium or vanadium oxide alone, but theimportance of its combination with the various other oxides in thevarious relationships mentioned is apparent when it is considered thatits conversion capacity. at 950 F. is only about 8% or 10% and at 1050F. is only about 20%. Thus it will be seen that the addition of one ofthe extending or dispersing oxides aluminum, zirconium 0r thoriumoxides, increases the activity'as much as to 30%, and the presence'ofzinc oxide prolongs the life perhaps two to three times as abovementioned.

With respect to the zinc oxide, it is possible that the zinc is presentas a complex oxide with the uranium or vanadium oxide, but I do not wishto be bound by any theory that the zinc definitely is present in' eitherof these forms or in some other form. The above disclosures arefurnished by way of illustration of the'generic invention, and are notto be construed as limiting beyond the scope of the claims, it beingobvious that various modification'smay be made within the ranges of theclaims by those skilled in the art.

I claim:

1. A catalyst substantially free from sulfate and comprising an oxidefrom the class consisting of uranium oxides and vanadium oxides, and agel-type disperser from the class consisting of aluminum oxide,zirconium oxide and thorium oxide, together with zinc oxide as anactivating agent.

2. A catalyst substantially free from sulfates and comprising uraniumoxide distributed in a gel-type carrier from the class consisting ofaluminum, zirconium and thorium oxides together with a substantialproportion of zinc oxide.

3. A catalyst comprising uranium oxide, zinc oxide and an oxide from theclass consisting of aluminum, zirconium and thorium oxide-gels whereinthe zinc oxide approximates 30-60% of .10 persing oxides such asaluminum or zirconium the catalyst and the other oxides are present inroughly equal molar proportions.

4. A catalyst comprising. a reduced form of uranium oxide in a carrieroxide or the class consisting of zirconium, thorium and aluminum oxidegels.

5. A catalyst according to claim 4 containing also zinc oxide.

6. A catalyst comprising roughly equal molar proportions of uraniumoxide, zinc oxide, and a dispersing agent from the class consisting ofaluminum, zirconium and thorium oxide-gels, together with a quantity ofvanadium oxide..

7. A catalyst comprising a reduced form of vanadium oxide in a carrieroxide of the class consisting of aluminum, thorium, and zirconiumoxide-gels, and a quantity of zinc oxide.

8. A catalyst comprising vanadium oxide, zinc oxide and an oxide fromthe class consisting of aluminum zirconium and thorium oxide-gelswherein the zinc oxide approximates 30-60% of the catalyst and the otheroxides are present in roughly equal molar proportions.

9. A catalyst comprising a reduced form of vanadium oxide, zinc oxideand an oxide from the class consisting of aluminum, zirconium andthorium oxide-gels, each of the three oxides being present insubstantial quantities.

10. A catalyst comprising a reduced form of uranium oxide, zinc oxideand an oxide from the class consisting of aluminum, zirconium'andthorium oxide-gels, each of the three oxides being present insubstantial quantities.

11. A catalyst substantially free from sulfates,

comprising a zirconium oxide gel carrier, uranium oxide carried by thegel as an active constituent, and zinc oxide.

12. A catalyst according to claim 11 in which each of the three oxidesis present in substantially equal molar proportions.

13. A catalyst comprising a zirconium oxide gel carrier, an active agentcarried thereby selected from the class consisting of uranium oxides andvanadium oxides, and zinc oxide as a third constituent, the constituentsbeing present in roughly equal molar proportions.

14. A catalyst substantially free fromsulfates comprising a gel typecarrier of the class consisting of aluminum oxide, zirconium oxide andthorium oxide, an active catalyst carried thereby selected from theclass consisting of uranium life.

WALTER F. HUPPKE.

